Polyamine brightening agent

ABSTRACT

A zinc electroplating bath includes zinc ions and a brightening agent. The brightening agent is a polyamine or a mixture of polyamines that include a quaternary ammonium group.

RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.60/550,167, filed Mar. 3, 2004 and which is incorporated herein byreference.

TECHNICAL FIELD

The present invention relates to a polyamine, and, more particularly, apolyamine brightening agent for an electroplating bath.

BACKGROUND

U.S. Pat. No. 4,889,602 discloses an alkaline zinc-nickel electroplatingbath, which comprises an aliphatic amine or polymer of an aliphaticamine in combination with an hydroxyaliphatic carboxylic acid.

U.S. Pat. Nos. 4,071,418 and 4,071,419 disclose the combination ofamines with substituted pyridines, such as nicotinic acid ornicotinamide for a zinc bath.

U.S. Pat. No. 5,417,840 discloses an alkaline zinc-nickel plating bathcomprising the combination of a polyamine, such as polyethyleneimine, incombination with an aromatic heterocyclic nitrogen containing compoundsuch as a sulfo-betaine, (e.g., pyridinium-N-propane-3-sulfonic acid);or a pyridinium chloride, such as N-carboxymethyl pyridinium chloride.

U.S. Pat. Nos. 4,210,500 and 4,730,022 disclose the use of an aromaticcarboxyl compound such as 1-benzyl-pyridinium-3-carboxylate or3-pyridine carboxylic acid (nicotinic acid) as a supplementarybrightener in an alkaline zinc bath. The carboxyl compounds are used incombination with a primary brightener, such as the reaction product of apolyamine and a sulfonate.

U.S. Pat. No. 5,405,523 discloses a zinc alloy electroplating bathcomprising a ureylene quaternary ammonium polymer as a brighteningagent. The quaternary ammonium polymer can include units of the generalformula:

where A may be O, S, or N, and R may be, inter alia, methyl, ethyl, orisopropyl. In the preferred polymers, these units are linked by unitsderived from, for example, a bis(2-haloethyl)ether, a(halomethyl)oxirane or a 2,2′-(ethylenedioxy)-diethylhalide.

U.S. Pat. No. 5,435,898 describes polymers for use as additives in theelectrodeposition of zinc and zinc alloys. The polymers have the generalformula:

where R₁ to R₄ may be the same or different and are, inter alia, methyl,ethyl, or isopropyl and Y may be S or O, and R₅ is an ether linkage,such as (CH₂)₂O(CH₂)₂.

U.S. Pat. No. 6,652,728 describes polymers for use as additives in theelectrodeposition of zinc or zinc alloys. The polymers have the generalformula:

U.S. Patent Application Publication No. 2003/0192785 describes anadditive for zinc or zinc alloy electroplating bath medium. The additivecomprises a random copolymer comprising the reaction product of one ormore ditertiary amines including an amide or thioamide functional group,and optionally one or more saturated or unsaturated ditertiary amineswith one or more saturated or unsaturated linking agents capable ofreacting with the ditertiary amines.

SUMMARY OF THE INVENTION

The present invention relates to a zinc or zinc alloy electroplatingbath. The electroplating bath includes zinc ions and a brighteningagent. The brightening agent comprises at least one polyamine or amixture of polyamines. The at least one polyamine or mixture ofpolyamines includes a first repeating unit that has the general formula:

and a second repeating unit selected from the group consisting of

and combinations thereof;

where Δ₁ is O, N, or S; Δ₂ is O, N, or S, and Δ₂ is not the same as Δ₁(i.e., Δ₂≠Δ₁); x is an integer from 2 to 6; y is an integer from 1 to 6;z is an integer from 1 to 6; R₁, R₂, R₃, and R₄, which may be the sameor different, is methyl, ethyl, isopropyl, n-propyl, hydroxyethyl, or—CH₂CH₂(OCH₂CH₂)_(m)OH; m is a number between 0-6; R₅ represents a groupof atoms necessary to complete a heterocyclic compound having a five orsix membered ring containing at least two nitrogen atoms, and R₆ isnothing or an alkyl group.

Another aspect of the present invention relates to a brightening agentfor an alkaline zinc or zinc alloy electroplating bath. The brighteningagent comprises a copolymer of a first monomer having the followingformula:

and at least two of the following compounds selected from the groupconsisting of:

where Δ₁ is O, N, or S; Δ₂ is O, N, or S, and Δ₂ is not the same as Δ₁(Δ₂≠Δ_(l)); x is an integer from 2 to 6; R₁, R₂, R₃, and R₄, which isthe same or different, is methyl, ethyl, isopropyl, n-propyl,hydroxyethyl, or —CH₂CH₂(OCH₂CH₂)_(m)OH; m is a number between 0-6; R₅represents a group of atoms necessary to complete a heterocycliccompound having a five or six membered ring containing at least twonitrogen atoms; R₆ is nothing or an alkyl group; R₇ and R₈, which may bethe same or different, is an alkylene group; and X₁, X₂, and X₃, whichis the same or different, is a halogen.

BRIEF DESCRIPTION OF THE DRAWING

The foregoing and other aspects of the present invention will becomeapparent to those skilled in the art to which the present inventionrelates upon reading the following description with reference to theaccompanying drawing.

The FIGURE is a schematic illustration of “Jiggle Cell” panel used in aplating test in accordance with the present invention.

DETAILED DESCRIPTION

The present invention relates to a brightening agent for a zinc or zincalloy electroplating bath (e.g., alkaline zinc or zinc alloyelectroplating bath). The electroplating bath can be used to form zincor zinc alloy coatings on electrically conductive substrates, which areprovided in the electroplating bath. Examples of electrically conductivesubstrates that can be electroplated include iron, ferrous basedsubstrates (e.g., iron alloys and steel), aluminum, aluminum alloys,magnesium, magnesium alloys, copper, copper alloys, nickel, nickelalloys, zinc, and zinc alloys. The brightening agent provides theelectrodeposited zinc or zinc alloy coatings with improved brightnessand leveling as well as mitigates blistering of the zinc or zinc alloycoatings.

The brightening agent of the present invention comprises a polyamine ora mixture of polyamines that are soluble in the electroplating bath. Thepolyamine or mixture of polyamines include one or more quaternaryammonium groups and/or secondary amines. More specifically, thepolyamine and mixture of polyamines include a first repeating unit thathas the general formula:

where Δ₁ is O, N, or S, x is an integer from 2 to 6, y is an integerfrom 1 to 6, R₁, R₂, R₃, and R₄, which may be the same or different, ismethyl, ethyl, isopropyl, n-propyl, hydroxyethyl, or—CH₂CH₂(OCH₂CH₂)_(m)OH, and m is a number between 0-6; and a secondrepeating unit selected from group consisting of:

where Δ₁ is defined as above, x is an integer from 2 to 6, z is aninteger from 1 to 6, and R₁, R₂, R₃, and R₄, are defined as above;

where Δ₂ is O, N, or S, and Δ₂ is not the same as Δ₁ (i.e., Δ₂≠Δ₁), x isan integer from 2 to 6, y is an integer from 1 to 6, and R₁, R₂, R₃, andR₄ are defined as above;

where R₅ represents a group of atoms necessary to complete aheterocyclic compound having a five or six membered ring containing atleast two nitrogen atoms (e.g., piperazine, imidazole, pyrazole, andpyrazine), R₆ is nothing or an alkyl group, and y is an integer from 1to 6 (e.g., methyl, ethyl, isopropyl, and butyl); and combinationsthereof.

The polyamine or mixture of polyamines can be formed, for example, in acondensation reaction from a ditertiary amine monomer of the generalformula:

where Δ₁ is defined as above, x is an integer from 2 to 6, and R₁, R₂,R₃, and R₄, are defined as above (e.g.,N,N′-bis-(3-(dimethylamino)propyl)urea,N,N′-bis-(3-(dimethylamino)propyl)guanidine, andN,N′-bis-(3-(dimethylamino)propyl)thiourea); and at least two of thefollowing monomers or linking agents:

where Δ₂ is defined as above, x is an integer from 2 to 6, and R₁, R₂,R₃, and R₄ are defined as above (e.g.,N,N′-bis-(3-(dimethylamino)propyl)urea,N,N′-bis-(3-(dimethylamino)propyl)guanidine, andN,N′-bis-(3-(dimethylamino)propyl)thiourea);

where R₅ and R₆ are defined as above, (e.g., piperazine, imidazole,pyrazole, and pyrazine);

X₁—R₇—X₂   (4C)

where X₁ is a halogen, such as Cl, Br, or I, X₂ is a halogen, such asCl, Br, or I, and R₇ is an alkylene group, such as methylene, ethylene,propylene, or butylene (e.g., ethylene dibromide and trimethylenechlorobromide (TMCB)) ; and

where R₈ is an alkylene group, such as methylene, ethylene, propylene,or butylene and X₃ is a halogen, such as Cl, Br, or I (e.g.,epichlorohydrin).

The polyamine or mixture of polyamines that are used to form thebrightening agent in accordance with the invention can have an averagemolecular weight of about 350 to about 10,000. By way of example, theaverage molecular weight of the polyamine or mixture of polyamines isabout 2000 to about 5000.

In an aspect of the invention, the brightening agent can comprise amixture of a first polyamine and a second polyamine. The first polyaminecan include the first repeating unit (1) and have the general formula:

where Δ₁ is defined as above, x is an integer from 2 to 6, y is aninteger from 2 to 6, R₁, R₂, R₃, and R₄, are defined as above, and n isan integer from 2 to 20.

The first polyamine can be prepared by first forming a ditertiary aminemonomer of the formula (3). The ditertiary amine monomer can be thecondensation product of a ditertiary amine containing one tertiary aminegroup and either one primary or one secondary amine group (e.g.,dimethylaminopropylamine (DMAPA)) and one mole of urea, thiourea, orguanidine. Examples of this ditertiary amine monomers includeN,N′-bis-(3-(dimethylamino)propyl)urea,N,N′-bis-(3-(dimethylamino)propyl)guanidine, andN,N′-bis-(3-(dimethylamino)propyl)thiourea.

This monomer can be reacted in a second condensation reaction with analkylene dihalide, such as ethylene dihalide (e.g., ethylene dichlorideor ethylene dibromide), propylene dihalide (e.g.,trimethylenechlorobromide (TMCB)), and butylene dihalide. Other alkylenedihalides can also be used.

The second condensation reaction gives the first polyamine of formula(5). An example of a specific polymer has the following formula:

The second polyamine that is mixed with the first polyamine to form thebrightening agent can include at least one of the second repeating units(2A, 2B, and/or 2C). An example of a second polyamine comprising thesecond repeating unit has the general formula:

where Δ₁ is defined as above, x is an integer from 2 to 6, z is aninteger from 1 to 6, R₁, R₂, R₃, and R₄, are defined as above, and n isan integer from about 2 to 20.

This second polyamine, like the first polyamine, can be prepared byreacting a ditertiary amine monomer, such as the ditertiary aminemonomer of the formula (3) (e.g.,N,N′-bis-(3-(dimethylamino)propyl)urea,N,N′-bis-(3-(dimethylamino)propyl)guanidine, andN,N′-bis-(3-(dimethylamino)propyl)thiourea). in a condensation reactionwith a haloalkyl oxirane, such as 1-chloro-2,3-epoxy-propane (i.e.,epichlorohydrin) or 1-choro-3,4-epoxy butane, to form the secondpolyamine of the formula (7). An example of a specific polyamine has theformula:

Another example of a second polyamine that can be mixed with the firstpolyamine to form an additive in accordance with the present inventionhas the general formula:

where Δ₂ is defined as above, x is an integer from 2 to 6, y is aninteger from 1 to 6, and R₁, R₂, R₃, and R₄ are defined as above, and nis a number between about 2 and about 20.

This second polyamine, like the first polyamine, can be prepared by acondensation reaction from a ditertiary amine monomer, such as theditertiary amine monomer of the formula (4A). Examples of specificditertiary amine monomers that can be used to form the second polyaminewill depend on the specific ditertiary amine monomer used to form thefirst polyamine, but can include N,N′-bis-(3-(dimethylamino)propyl)urea,N,N′-bis-(3-(dimethylamino)propyl)guanidine, andN,N′-bis-(3-(dimethylamino)propyl)thiourea.

The ditertiary amine monomer can be reacted in a condensation reactionwith an alkyl dihalide (e.g., TMCB) to form a polyamine that has thegeneral formula (9). An example of a specific polyamine formed by thecondensation reaction has the following formula:

The first polyamine and the second polyamine can be mixed together toform the brightening agent in accordance with the present invention. Forexample, the additive can comprise a mixture of a first polyamine thathas the formula (6) and a second polyamine that has the formula (8). Inanother example, the additive can comprise a mixture of a firstpolyamine that has the formula (6) and a second polyamine that has theformula (10).

The ratio of the first polyamine to the second polyamine used to formthe brightening agent in accordance with the present invention can bevaried as desired to influence the properties of the electrodepositedcoating produced by the electroplating bath. Typically, a brighteningagent that includes a higher molar ratio of the guanidino orheterocyclic groups when used in a electroplating bath of the presentinvention, can provide a brighter deposit or coating. The deposit orcoating with the higher molar ratio of guanidino or heterocylic groupscan have a poorer metal distribution. In contrast, brightening agentsthat include a higher molar ratio of urea groups can have an improvedmetal distribution, but not be as bright. The molar ratio of the firstpolyamine to second polyamine included in the brightening agent cantherefore be adjusted to influence the properties of the brightening andbe, for example, from about 1 to about 10 to about 10 to about 1. Thismolar ratio can be higher or lower depending on the specific propertiesdesired.

The brightening agent can include other polyamines in addition to thefirst polyamine and the second polyamine described above. The additionalpolyamines can comprise at least one of the second repeating units, suchas one of the repeating units not used to form the second polyamine, aswell as additional repeating units.

Optionally, instead of mixing the first polyamine with the secondpolyamine to form the brightening agent in accordance with the presentinvention, the first polyamine can be copolymerized with the secondpolyamine to form a block copolymer. The block copolymer can include afirst block comprising the first repeating unit (1) and a second blockthat comprises the second repeating unit (e.g., 2A, 2B, or 2C). Theblock copolymer can be formed, for example, by initially preparing thefirst polyamine and the second polyamine with terminal amine groups, andthen reacting the first polyamine and the second polyamine with alinking agent, such as an alkylene dihalide or haloalkyl oxirane. Itwill be appreciated that the first polyamine and the second polyaminecan be copolymerized using other linking agents and by other reactionmethods.

In another aspect of the invention, the first repeating unit and thesecond repeating unit can be provided in the polymer chain of the samepolyamine copolymer. The polyamine copolymer can be a random copolymer(or statistical copolymer), where the first repeating unit and the atleast one second repeating unit are distributed randomly in the polymerchain, an alternating copolymer, where the first repeating unit and theat least one second repeating unit are distributed in a regularalternating fashion in the chain, or a block copolymer, where a longsequence or block of the first repeating unit and the at least onesecond repeating unit are joined to a block of the at least one secondrepeating unit.

One example of a copolymer includes a first repeating unit of theformula (1) and a second repeating unit of the formula (2A). Thecopolymer can be prepared by polymerizing a ditertiary amine mononomerof the formula (3) (e.g., N,N′-bis-(3-(dimethylamino)propyl)urea,N,N′-bis-(3-(dimethylamino)propyl)guanidine, andN,N′-bis-(3-(dimethylamino)propyl)thiourea) with an alkyl dihalide(e.g., TMCB) and an haloalkyl oxirane (e.g., epichlrohydrin) as shown inthe following reaction scheme:

where Δ₁ is defined as above, x is an integer from 2 to 6, R₁, R₂, R₃,and R₄, are defined as above, X₁ is a halogen, such as Cl, Br, or I, X₂is a halogen, such as Cl, Br, or I, R₇ is an alkylene group, such asmethylene, ethylene, propylene, or butylene, R₈ is an alkylene group,such as methylene, ethylene, and propylene, and X₃ is a halogen, such asCl, Br, or I.

In this example, the ditertiary amine monomer of formula (3) (e.g.,N,N′-bis-(3-(dimethylamino)propyl)urea,N,N′-bis-(3-(dimethylamino)propyl)guanidine, andN,N′-bis-(3-(dimethylamino)propyl)thiourea) can be initially mixed andreacted in a first condensation reaction with the alkylene dihalide(e.g., TMCB). After allowing the first ditertiary amine and the alkylenedihalide to at least partially react, the haloalkyl oxirane (e.g.,epichlorhydrin) can be added to the reaction mixture to complete thereaction and form the copolymer. Alternatively, the ditertiary aminemonomomer can be initially mixed and reacted in a first condensationreaction with the haloalkyl oxirane (e.g., epichlorohydrin). Afterallowing the ditertiary amine monomer and the haloalkyl oxirane to atleast partially react, the alkylene dihalide (e.g., TMCB) can be addedto the reaction mixture to complete the reaction and form the copolymer.

The molar ratio of the first repeating unit (1) relative to the secondrepeating unit (2) in this copolymer can be varied by varying the molarratios of alkylene dihalide and haloalkyloxirane used in the reaction.Varying the molar ratio of the alkylene dihalide to the haloalkyloxirane in the reaction can influence the properties of theelectrodeposited coating produced by the electroplating bath. Increasingthe molar ratio of the haloalkyl oxirane to the alkylene dihalideresults in a brightening agent that provides an improved grain refiningeffect to a deposit or coating. Increasing the molar ratio of thehaloalkyl oxirane to the alkylene dihalide, however, reduces theefficiency of the electroplating bath. Accordingly, the molar ratio ofthe haloalkyl oxirane to alkylene dihalide used to form the brighteningagent can be, for example, about 1 to about 10, to about 10 to about 1.It should be appreciated that this molar ratio can be higher or lowerdepending on the specific properties desired.

Another example of a copolymer used to form a brightening agent inaccordance with the present invention includes a first repeating unit ofthe formula (1) and a second repeating unit of the formula (2B). Thecopolymer can be prepared by polymerizing the ditertiary amine mononomerof formula (6) (e.g., N,N′-bis-(3-(dimethylamino)propyl)urea) and aditertiary amine mononomer with formula (10) (e.g.,N,N′-bis-(3-(dimethylamino)propyl)guanidine) with an alkylene dihalide(e.g., TMCB) as shown in the following reaction scheme:

In this example, the N,N′-bis-(3-(dimethylamino)propyl)urea) and theN,N′-bis-(3-(dimethylamino)propyl)guanidine can be initially mixed. Themixture can then be reacted in a condensation reaction with the alkylenedihalide (e.g., TMCB) to complete the reaction and form the copolymer.

The molar ratio of the N,N′-bis-(3-(dimethylamino)propyl)urea) to theN,N′-bis-(3-(dimethylamino)propyl)guanidine used to form this copolymercan be varied to influence the properties of the electrodepositedcoating produced by the electroplating bath. Increasing the molar ratioof the N,N′-bis-(3-(dimethylamino)propyl)guanidine to theN,N′-bis-(3-(dimethylamino)propyl)urea) results in a brightening agentthat provides a brighter deposit or coating, but a less uniform depositor coating (i.e., less uniform metal distribution). Conversely,increasing the molar ratio of theN,N′-bis-(3-(dimethylamino)propyl)urea) to theN,N′-bis-(3-(dimethylamino)propyl)guanidine results in a brighteningagent that provides a more uniform deposit or coating distribution, buta less bright (or duller) deposit. Accordingly, the molar ratio of thethe

N,N′-bis-(3-(dimethylamino)propyl)urea) to theN,N′-bis-(3-(dimethylamino)propyl)guanidine used to form this copolymercan be varied, for example, from about 1 to about 10 to about 10 toabout 1. It will be appreciated that this molar ratio can be higher orlower depending on the specific properties desired.

Yet another example of a copolymer used to form a brightening agent inaccordance with the present invention includes a first repeating unit ofthe formula (1) and a second repeating unit of the formula (2C). Thecopolymer can be prepared by polymerizing the ditertiary amine mononomerof the formula (3) (e.g., N,N′-bis-(3-(dimethylamino)propyl)urea) and aheterocyclic amine monomer of the formula (4B) (e.g., piperazine,imidazole, pyrazole, and pyrazine) with a alkylene dihalide (e.g., TMCB)as shown in the following reaction scheme:

In this example, the ditertiary amine monomomer of formula (3) and theheterocyclic amine monomer of the formula (4B) (e.g., piperazine,imidazole, pyrazole, and pyrazine) can be initially mixed. The mixturecan then be reacted in a condensation reaction with the alkylenedihalide (e.g., TMCB) to complete the reaction and form the copolymer.

The molar ratio of the ditertiary amine monomer of formula (4) to theheterocyclic amine monomer (4B) used to form this copolymer can bevaried to influence the properties of the electrodeposited coatingproduced by the electroplating bath. Increasing the molar ratio of theheterocyclic amine monomer to the ditertiary amine monomer can result ina brightening agent that provides a brighter deposit or coating, but canprovide a less efficient electroplating bath. Accordingly, as with theother copolymers, the molar ratio of the ditertiary amine monomer to theheterocyclic amine monomer used to form this copolymer can be varied,for example, from about 1 to about 10 to about 10 to about 1. It will beappreciated that this molar ratio can be higher or lower depending onthe specific properties desired.

Still another example of a copolymer used to form a brightening agent inaccordance with the present invention includes a first repeating unit ofthe formula (1), a second repeating unit of the formula (2A), and asecond repeating unit of the formula (2C). The copolymer can be preparedby polymerizing the ditertiary amine mononomer of the formula (3) (e.g.,N,N′-bis-(3-(dimethylamino)propyl)urea) and a heterocyclic amine monomerof the formula (4B) (e.g., piperazine, imidazole, pyrazole, andpyrazine) with a alkylene dihalide (e.g., TMCB) and a haloalkyloxirane(e.g., epichlorhydrin) as shown in the following reaction scheme:

In this example, the ditertiary amine monomer of formula (3) and theheterocyclic amine monomer of the formula (4B) can be initially mixed.The mixture can then be reacted in a condensation reaction with thealkylene dihalide (e.g., TMCB). After allowing the ditertiary aminemonomer, the heterocyclic monomer, and the alkylene dihalide to at leastpartially react, the haloalkyl oxirane (e.g., epichlorhydrin) can beadded to the reaction mixture to complete the reaction and form thecopolymer.

The molar ratio of the heterocylic amine monomer, ditertiary aminemonomer, haloalkyl oxirane, and alkylene dihalide can all be adjusted,as discussed above, to affect the properties of the brightening agentand the electrodeposited coating. Accordingly, the molar ratios of theheterocylic amine monomer, ditertiary amine monomer, haloalkyl oxirane,and alkylene dihalide can be 1:1:1:1 or another ratio depending on theparticular properties desired.

The amount of the brightening agent comprising the polyamine or mixtureof polyamines of the present invention added to an electroplating bathis a brightening amount. Typically, the brightening agent can be addedto the electroplating bath in an amount of about 50 to about 2,000 ppm(about 0.05 grams per liter to about 20 grams per liter) based on theweight of the bath.

The electroplating bath contains a controlled amount of zinc ions andoptionally a controlled amount of one or more additional metal ions,which can alloy with the zinc to produce a desired result. The alloyingmetal ions that can be used in the present invention are from the firsttransition of the Periodic Table. Nickel, cobalt, iron, and combinationsthereof are commonly used alloying materials, which are particularlyuseful in the present invention. Other examples of alloying metals thatcan be used in the present invention include manganese and chromium.

For an alkaline electroplating bath, zinc ions are usually provided bymeans of a zinc compound in combination with a strong base. The zinccompound can be any zinc compound that is soluble in an alkaline aqueousmedium. Examples of zinc compounds, which can be added to theelectroplating bath, are zinc oxide, or a soluble salt, such as zincsulfate, zinc carbonate, zinc sulfamate, and zinc acetate. Theconcentration of zinc ions in the electroplating bath can be from about1 to 100 grams per liter, preferably about 4 to about 50 grams per liter(about 4,000 to about 50,000 ppm).

The pH of the alkaline plating bath can be from about 9 to about 13 orhigher, such as above about 14. At a pH above about 14, the predominantzinc species in the bath is the zincate ion. The bath contains a base inan effective amount to achieve this pH. Amounts of from about 50 gramsper liter to about 200 grams per liter, based on the electroplatingbath, of the base can be used. Examples of bases that can be used arealkali metal derivatives, such as sodium hydroxide, potassium hydroxide,sodium carbonate, and potassium carbonate.

Normally, the alkaline bath is prepared by dissolving the zinc oxide orzinc salt in a commercially available caustic solution and thenadjusting the concentration of the solution to that desired by addingwater to the solution. For instance, 10 grams of zinc oxide can bedissolved in 75 ml of a 50% caustic solution, which is then diluted tothe desired volume percent by the addition of water. If desired, the pHof the bath can be adjusted by adding to the bath the parent base of thezinc salt, or another base, such as sodium or potassium carbonate.

The concentration of the zinc ions in the bath, for an electroplatingbath, can vary in accordance with conventional practice. The zinc ionconcentration typically ranges from about 4,000 ppm (about 4 grams perliter) to about 50,000 ppm (about 50 grams per liter). For an acid bath,the concentration of zinc ions typically is at the high end of thisrange.

The alloying metal ions can also be introduced into the bath in the formof an oxide or sulfate in the case of an alkaline bath or in the form ofan aqueous soluble salt, such as a chloride, sulfate, fluoroborate,acetate, or sulfamate, in the case of an acid bath. The concentrationrange of the alloying metal ions, in the practice of the presentinvention, typically is in the range between about 20 ppm to about20,000 ppm (about 0.02 to about 20 grams per liter). Theseconcentrations refer to the amount of metal ions contained in the bath.The amounts of the salts of these metals to be used in each case aredetermined by appropriate calculation.

If combinations of alloying metals are used, each alloying metal can bepresent in the range of about 20 ppm to about 20,000 ppm. Normally, theamount of alloying metal ions in the bath will be in the weight rangenecessary to produce, in the plate which is deposited, about 0.1%-15% byweight alloying element. Additionally, since with different types ofalloys a different proportion of alloy is also necessary in order forexample to improve the corrosion protection, this concentration can bedifferent from metal ion to metal ion.

In addition to the use of a polyamine or mixture of polyamine of thepresent invention, the electroplating bath can contain, as asupplemental brightener, conventional brighteners, such as sodiumsaccharin, anisic aldehyde, polyvinyl alcohol, polyethyleneimine,N-benzyl nicotinic acid (sodium salt), the reaction product ofepichlorohydrin with an amine, and an aromatic aldehyde. Thesesupplemental brighteners can be used in the bath of the presentinvention in conventional amounts, in combination with the polyaminecompound of the present invention.

Other supplemental brighteners that can be used in the bath aredescribed in U.S. Pat. No. 6,468,411 to Eckles et al. hereinincorporated by reference in its entirety. These supplementalbrighteners can include a pyridinium compound in which a lower alkyl,benzyl or naphthyl group or derivative thereof is substituted at thenitrogen atom of the pyridine ring and a group, which is either acarboxylate group or which can undergo alkaline hydrolysis to acarboxylate group is at the 3-position of the pyridine ring. Examples ofthese pyridinium compound brighteners can include1-benzylpyridinium-3-carboxylate, 1-benzylpyridinium-3-carboxamide,1-methylpyridinium-3-carboxylic acid (or salt thereof),1-methylpyridinium-3-carboxamide and combinations thereof.

The supplemental brightener can also comprise a low molecular weightaliphatic polyamine, such as one having a molecular weight less thanabout 300. An example of an aliphatic polyamine istetraethylenepentamine (TEPA), which has a molecular weight of about189. Another example of an aliphatic polyamine is pentaethylenehexamine(PEHA) which has a molecular weight of about 232.

It is also possible to use heptaethyleneoctamine (molecular weight about300) marketed by the Nippon Shokubai Co. Ltd. under the trademark“EPOMIN 003”. Also diethylenetriamine (molecular weight about 103) canbe used.

The bath can also comprise an aliphatic polyamine having a molecularweight above about 300 in combination with the low molecular weightaliphatic polyamine. An example of a higher molecular weight aliphaticpolyamines that can be used is quadradecaethylenepentadecamine(molecular weight 600) marketed by Nippon Shokubar Co. Ltd. under thetrademark “Epomin 006”.

The electroplating bath of the present invention can also include acomplexing agent, particularly if the baths according to the inventioncontain the aforementioned additional metal ions. Complexing agentsadapted to these additional metal ions can be added to the bath in orderto control the deposition potentials and permit a common reduction withthe zinc ions that are present. Examples of complexing agents that canbe added to an electroplating bath in accordance with the presentinvention are sorbitol, gluconic acid, heptanoic acid, tartaric acid,glycine, ethylenediamine tetraacetic acid, triethanolamine, saltsthereof, and combinations thereof.

Other complexing agents, such as chelate-forming agents, can also beused. Examples of chelate-forming agents include hydroxycarboxylatessuch as sodium gluconate, aminoalcohols such as triethanolamine,polyamines such as polyethylenediamine, aminocarboxylates such as EDTA,aminophosphonates such as aminotris(methylenephosphonic acid), andpolyhydric alcohols such as sorbitol or sucrose. The complexing agentmay be contained individually or as a mixture in the baths according tothe invention, the amount of the agent preferably being in the rangefrom 2 to 200 g/l.

The electroplating baths according to the invention may furthermorecontain known levelling agents such as 3-mercapto-1,2,4-triazole and/orthiourea, the latter being preferred. The concentration of the levellingagent is the normal concentration for use in zinc baths, and ranges forexample from 0.01 to 0.50 g/l. Further additives for the baths accordingto the invention include aromatic aldehydes or their bisulfite adducts.

Examples of aromatic aldehydes include 4-hydroxybenzaldehyde,4-hydroxy-3-methoxybenzaldehyde (vanillin), 3,4-dimethoxybenzaldehyde,3,4-methylenedioxybenzaldehyde, 2-hydroxybenzaldehyde and4-hydroxybenzaldehyde, or mixtures thereof. These additives, whoseconcentration is in the range from 0.005 to 1.0 g/l preferably from 0.01to 0.50 g/l, act in a manner known per se as brightening agents. Aparticularly preferred example of such a brightening agent is vanillinIn addition the bath according to the invention may also contain othersubstances that can be used as brightening agents, such as substancesselected from the group comprising sulfur compounds, aldehydes, ketones,amines, polyvinyl alcohol, polyvinyl pyrrolidone, proteins or reactionproducts of halogenated compounds with aliphatic or aromatic amines,polyamines or heterocyclic nitrogen compounds, and mixtures thereof.

The baths according to the invention may also contain a water-softener,since the sensitivity of the bath according to the invention to foreignmetal ions, in particular calcium and magnesium ions from tap water, isreduced by the use of such additives. Examples of such water-softenerare EDTA, sodium silicates and tartaric acid.

The electroplating baths of the present invention are used atconventional current densities, preferably about 1 to 100 amps persquare foot, as determined by Hull Cell evaluation. For example, thebath can be operated with an average cathode current density in therange of about 3 amps per square foot to about 25 amps per square foot,typically about 20 amps per square foot. The cathode current density isdependent upon the particular type of deposit desired. Bright depositscan be obtained at conventional temperatures, for instance about 20° C.to about 40° C.

The electrodeposition using the electroplating bath according to theinvention may, for example, be carried out as a drum galvanizing processwhen used for mass parts, and as a frame galvanizing process fordeposition on larger workpieces. In this connection anodes are used thatmay be soluble, such as for example zinc anodes, which at the same timeserve as a source of zinc ions so that the zinc deposited on the cathodeis recovered by dissolution of zinc at the anode. Alternativelyinsoluble anodes such as for example iron anodes may also be used,wherein the zinc ions removed from the electrolyte have to bereplenished in another way, for example by using a zinc dissolving tank.

The following examples are included to demonstrate various aspects ofthe invention. Those of skill in the art should, in light of the presentdisclosure, appreciate that many changes can be made in the specificaspects which are disclosed and still obtain a like or similar resultwithout departing from the spirit and scope of the invention.

EXAMPLES Example 1

113.8 g guanidine hydrochloride (GHC/1.19 mol) and 300 mL/243.6 gdimethylamino propylamine (DMAPA/2.38 mol) were mixed in a 1L threenecked flask equipped with a condenser, an internal thermometer, anelectric shaft stirrer, and an electric heating mantel. The guanidinehydrochloride dissolved immediately. The mixture was heated to refluxfor 8h. During this time the temperature rose to 210° C. and the colorchanged from colorless to amber. After cooling to room temperature ahighly viscous amber substance was obtained. The IR spectrum showed theexpected bands for the C═N bond and the different methyl and methylenegroups together with the NH-bands.

Example 2

The product obtained in Example 1 was reacted with TMCB in differentways to evaluate its possible use as a brightening agent.

In a first reaction, 43 g guanidine.DMAPA (0.19 mol) was mixed with 18.6mL TMCB (0.19 mol) in a flask with a magnetic stirrer and a condenser.The mixture was carefully heated. After approximately 10 minutes, themixture erupted and formed a yellow foam in the flask. This solidresidue was dissolved in 75 mL H₂O to give a about 50% solution. A verysmall amount of unreacted TMCB was recovered by phase separation. The IRspectrum of the dry product showed that the bands for the aminomethylgroups had shifted in the expected way and the band for the methylenegroups had increased in intensity and also shifted.

To determine the potential of the product as a brightener, a Hull celltest was performed. In the Hull cell test, 1 mL of the 50% solution wasadded to a Hull cell containing a solution of 11.5 g/L Zn, 1 mL XenitheANC WC (EDTA solution) and 0.2 mL Xenithe ANC Purifier (thioureasolution). A Hull cell panel was plated for 5 minutes at 3 A. The HullCell test yielded a bright panel with a thickness ratio of 1.7 betweenmeasurements taken at 2.5 and 7.5 cm from the left edge of the panel.

Example 3

This way of producing the polymer was not an option for industrialscale, and the metal distribution obtained with this material was notsatisfactory. A different experimental setup was therefore tested.

229 g guanidine.DMAPA (1 mol) were put into a three necked flask with aninternal thermometer, a shaft stirrer, a dropping funnel and a heatingmantel and heated to about 90° C.

157 g/98mL TMCB (1 mol) were added slowly over 35 minutes. During thistime, the temperature rose to about 170° C., and the mixture becameextremely viscous. After an additional 30 min the residue could nolonger be stirred. After cooling to room temperature, 386 mL of waterwere added to obtain an approx. 50% solution.

The IR spectrum was basically identical to that of the material obtainedbefore. A Hull Cell test, in accordance with the Hull Cell plating testof Example 2 (3 A/5 minutes), was performed using the material. The HullCell test yielded a bright panel. The thickness ratio of the deposit at2.5 and 7.5 cm from the left edge was determined to be r=1.8. Acomparative panel obtained with the reaction product of ureadmapa andTMCB in a 1:1 ratio was found to be only semi bright but with athickness ratio of r=1.2.

Example 4

The use of H₂O as a solvent of guanidine.DMAPA and TMCB wasinvestigated. 150 g of guanidine.DMAPA (0.66 mol) were dissolved in 170mL H₂O and heated to 80° C. 65 mL/103 g of TMCB (0.66 mol) were addedover 30 minutes. During this time, the temperature was allowed to riseto 100° C. and the mixture started to reflux. The mixture was refluxedfor 4 h while the temperature slowly rose to 105° C. After cooling toroom temperature, approximately 2 mL of unreacted TMCB were separated.

The IR spectrum of the yellow product was identical to the one obtainedfrom the reactions without solvent. A Hull Cell test, in accordance withthe Hull Cell plating test of Example 2 (3 A/5 minutes), was performedusing the material. The Hull Cell test yielded a semi bright panel. Thedegree of brightness of the other materials was not quite reached. Thethickness ratio between the points at 2.5 and 7.5 cm from the left edgewas determined to be r=1.7.

Example 5

To determine whether the pure metal distribution was affected by theunreacted TMCB, the reaction of guanidine DMAPA and TMCB was performedin a less polar solvent. Glycerol was selected because it is polarenough to dissolve the polymer, the boiling point is high enough toallow decent reaction rates and it has also been used as an additive inalkaline zinc plating. The latter reason would alleviate the obligationto remove the solvent.

150 g guanidine.DMAPA (0.66 mol) were dissolved in 130 ml of glyceroland the viscous mixture was heated to 90° C. 65 mL TMCB (0.66) wereslowly added over 2 h. The temperature rose rapidly to 160° C., and themixture turned dark. After cooling to room temperature an extremelyviscous brown substance was obtained and a small amount (8 mL) of acolorless liquid separated on top. The colorless liquid was identifiedas TMCB by IR. The brown residue dissolved only very slowly in water. Asmall amount of the material was added to a Hull cell. The plating testat 3A/5 min yielded a bright panel. The thickness ratio was determinedat r=1.5.

Example 6

Linking the guanidine.DMAPA with epichlorohydrin was investigated. 57 gguanidine.DMAPA (0.25 mol) were dissolved in 80 mL H₂O and heated to 70°C. 25 g/21 mL epichlorohydrin (0.27 mol) were added within 7 minuteswhile the temperature was allowed to rise to 101° C. and the solutionbegan to reflux. The solution was heated to reflux for 2¼ h more. Aftercooling to room temperature an amber solution was obtained.

The IR spectrum after evaporation of water corresponded to the materialsobtained from reaction with TMCB but additionally showed bands for C—OHgroups. A Hull Cell plating test, in accordance with the Hull Cellplating test of Example 2 (3 A/5 minutes), was performed using thematerial. The Hull Cell test yielded a bright panel over the wholecurrent density-range. The thickness ratio was determined to be r=1.7.

Example 7

The results of Examples 1-6 gave the impetus for the idea ofpolymerizing ureadmapa units with different linkers in one polymer. Thegeneral aspect obtained with the epichlorohydrin based polymer was animprovement in brightness as compared with the TMCB based polymers. Onthe other hand, the inhibiting effect was pronounced. It was thereforedecided to polymerize ureadmapa with TMCB and epichlorohydrin in onepolymer.

92 g ureadmapa (0.4 mol) were dissolved in 150 mL H₂O and the lightyellow solution was heated to 70° C. 31.5 g/20 mL TMCB (0.2 mol) wereadded within 5 minutes while the temperature was allowed to rise to 100°C. The solution was stirred at this temperature for 25 min and thencooled down to 65° C. within 30 minutes. 20.2 g/17 mL epichlorohydrinwere added within 10 minutes and the temperature was allowed to rise to85° C. The solution was then stirred for 2½ h at 70° C.-80° C. Aftercooling to room temperature, a viscous yellow liquid was obtained.

The IR spectrum of the material after evaporation of excess water wasvery similar to the product of the reaction with TMCB only.Additionally, some bands can be seen between 950 cm⁻¹ and 1150 cm⁻¹ thatcan be attributed to the additional C—OH functionality. A Hull Celltest, in accordance with the Hull Cell plating test of Example 2 (3 A/5minutes), was performed using the material. The Hull Cell test yielded apanel that was uniformly semi-bright over the whole current densityrange. The thickness ratio between measurements taken at 2.5 and 7.5 cmfrom the left edge of the panel was r=1.1 with a very decent efficiency.

This result was very encouraging since it yielded a material that gave agood metal distribution together with a moderate degree of brightness.Generally speaking the brightness obtained with this molecule can beconsidered a substantial improvement as compared to Mirapol WT. Theextreme effect observed with the epi-only derivative was not observedand it might be interesting to see if there is an influence of thereaction sequence on the performance of the material.

Example 8

Tests were performed to determine a TMCB/epichlorohydrin ratio thatpreserves the superior brightness as compared to Mirapol WT and stillgives satisfactory current efficiency. To test this, ureadmapa wasreacted with TMCB and epichlorohydrin in a 3/1 ratio.

115 g ureadmapa (0.5 mol) were dissolved in 190 mL H₂O and heated to 70°C. 59 g/37 mL TMCB (0.375 mol) were added within 20 min and the solutionwas refluxed for 35 minutes at 100° C. The mixture was then cooled to60° C. in 20 minutes. 13 g/11 mL epichlorohydrin (0.14 mol) were addedin 6 min and the temperature was allowed to rise to 70° C. The mixturewas then stirred for 1¼ h at 60-70° C. After cooling to roomtemperature, a nearly colorless viscous solution was obtained.

The IR spectrum of the material showed a pattern in the region between900 and 1200 cm⁻¹ that lies between the one observed for the reactionproduct of ureadmapa and TMCB (1:1 ratio) and the one for the 1/1reaction product.

A Hull Cell test, in accordance with the Hull Cell plating test ofExample 2 (3 A/5 minutes), was performed using the material. The HullCell test yielded a panel that was semi-bright to bright over the wholecurrent density range. The general aspect is comparable to the 1/1reaction product. The thickness ratio was determined as r=1.3. Atcomparable concentration, the efficiency was found to be nearly twice ashigh as the efficiency with the 1/1 product.

Seemingly the drawbacks of the use of epichlorohydrin can be overcome byincreasing the TMCB/epichlorohydrin ratio in the reaction whileretaining some of the advantages.

Example 9

A class of polymers that gives very bright Zn deposits are the onesbased on piperazine epichlorohydrin reactions. It was determined whetherpiperazine can be copolymerized with ureadmapa to give bright depositsand if piperazine is nucleophilic enough to react with TMCB.

57.5 g ureadmapa (0.25 mol) and 4.3 g piperazine (0.05 mol) weredissolved in 75 mL H₂O and heated to 80° C. 47.2 g/29.5 mL TMCB (0.3mol) were added in 20 min while the temperature was allowed to rise to103° C. The solution was refluxed at 100-104° C. for 2 h. The IRspectrum of the material after evaporation of excess water resembled theone for the reaction product of ureadmapa and TMCB (1:1 ratio). Anadditional band at 2709 cm⁻¹ was observed that was assigned to thepiperazine unit.

Example 10

A further candidate for copolymerization that might contribute to theoverall brightness was imidazole. Imidazole epichlorohydrin polymers areknown brightening additives for Zn baths. Additionally, imidazoleprovides at least one tertiary amine nitrogen per molecule that shouldbe nucleophilic enough to react with TMCB.

115 g ureadmapa (0.5 mol) and 6.8 g imidazole (0.1 mol) were dissolvedin 220 mL H₂O and heated to 95° C. 94 g/59 mL were added in 30 minutes.The solution was refluxed at 97-100° C. for 2 h. After cooling to roomtemperature, a nearly colorless, viscous solution was obtained.

The IR spectrum of the material resembled the spectrum of the reactionproduct of ureadmapa and TMCB (1:1 ratio) with an additional band at2726 cm⁻¹.

A Hull Cell plating test was performed in accordance with the Hull Cellplating test of Example 1 (3 A/5 minutes) using the material. The Hullcell test yielded a panel that was bright to semi bright over the wholecurrent density range. The thickness ratio (2.5 cm/7.5 cm) wasdetermined as r=1.4 with satisfactory efficiency. A second test wasperformed at 1 A for over 15 minutes. Here the aspect of the panel wassemi-bright with stripes in the middle current density area. Thethickness ratio in this case was determined as r=2.1. The maindifference between these two tests was that in the 3 A case a strongeragitation of the bath takes place due to the stronger gas evolution onthe cathode. Therefore a Hull cell test was run at 1 A /5 min withmechanical agitation of the bath. Under these conditions the thicknessratio was found to be r=1.2.

Example 11

An approach to further improve the properties of the imidazole additionmay lie in the use of epichlorohydrin as an additional linking agent. Inmany cases these products gave improved brightness and the polarizingeffect of these products have been proven in the experiments describedabove.

115 g ureadmapa (0.5 mol) and 6.8 g imidazole (0.1 mol) were dissolvedin 210 mL H₂O and heated to reflux at 98° C. 70.8 g /44 mL TMCB wereadded in 20 min and the mixture was refluxed for 1 h. Afterwards thesolution was cooled to 62° C. in 20 min and 15.3 g/12.9 mLepichlorohydrin (0.165 mol) were added within 5 minutes. The mixture wasthen stirred at 60° C.-70° C. for 2 h. After cooling to roomtemperature, a nearly colorless, viscous solution was obtained.

The IR spectrum of the material after evaporation of excess water wassimilar to the one obtained without adding epichlorohydrin, but the bandat 2726 cm⁻¹ was missing and some shoulders for the C—OH bands could beseen between 950 and 1150 cm⁻¹.

Hull Cell tests, in accordance with the Hull Cell plating test ofExample 2 (3 A/5 minutes), were performed using the material atdifferent concentrations and different current densities generallyyielded panels that were semi bright to bright and showed thicknessratios of r=1.2-1.5. The current efficiency was found to be somewhatlower than with the TMCB-only polymer but still acceptable.

Example 12

In a comparative test Jiggle cell panels were plated under the followingconditions:

-   10.5 g/L Zn, 120 g/L NaOH, 10 mL/L 0.2 M benzyl pyridinium    carboxylate, 3 A, 30′    -   1) 10 mL/L Mirapol WT (10%)    -   2) 10 mL/L the reaction product of ureadmapa and TMCB (1:1)        (10%)    -   3) 10 mL/L the imidazole copolymer of Example 10 (12%)    -   4) 10 mL/L the imidazole copolymer of Example 11 (12%)

The dilutions were chosen to obtain the same concentrations of thepolymers in the bath on a weight/volume basis. The panels were flattenedafter plating and set aside for evaluation of latent blistering.

The FIGURE shows the position on the panels where the thickness of thedeposit was determined by XRF. The following Table shows the thicknessmeasurements taken at these positions and the thickness ratio betweenthe highest and lowest on the front side (3/2) and the highest on thefront and the lowest on the back (3/6).

TABLE Polymer 1/μin 2/μin 3/μin 4/μin 5/μin 6/μin 3/2 3/6 WT 379 287 384293 474 299 1.34 1.31 Ureadmapa/ 324 322 343 299 444 301 1.07 1.15 TMCBEX 10 433 379 442 365 463 351 1.17 1.26 EX 11 335 306 356 175 438 2921.17 1.22 (?)

The following conclusions can be drawn from this experiment. Concerningthe aspect, the imidazole copolymer of Example 10 was judged to give thebest brightness followed by the reaction product of ureadmapa and TMCB.Mirapol WT gives the least appealing aspect of the four polymers. Underthe given conditions Mirapol WT gives the worst metal distribution whilereaction product of ureadmapa and TMCB gives the best. Both theimidazole copolymer of Example 10 and the imidazole copolymer of Example11 gave metal distributions in between but closer to the reactionproduct of ureadmapa and TMCB. It is noteworthy that the imidazolecopolymer of Example 10 gives the best overall efficiency.

Example 13

The copolymerization of ureadmapa and guanadmapa was investigated. Thisshould combine the superior brightness of the guanadine polymers withthe superior metal distribution properties of the urea polymers.

In a first experiment 57.5 g ureadmapa (0.25 mol) and 57.3 g guanadmapa(0.25 mol) were dissolved in 195 mL H₂O and heated to 67° C. 78.7 g/49.2mL TMCB were added within 13 minutes and the mixture was refluxed for 2h at 98-100° C. After cooling to room temperature a clear, colorless,viscous liquid was obtained.

The IR spectrum showed a pattern that could easily be interpreted as amixture of reaction product of ureadmapa and TMCB and the guanidinepolymer obtained before. The band at 1643 cm⁻¹ is much stronger than theone at 1561 cm⁻¹, which is due to the presence of the N═C besides theO═C double bond.

A Hull Cell test, in accordance with the Hull Cell plating test ofExample 2 (3 A/5 minutes), was performed using the material. The HullCell test yielded a panel that is semi-bright to bright. The aspect wassimilar to the guanidine product than to the reaction product ofureadmapa and TMCB. Also, the metal distribution seems to be influencedmore by the guanidine function. The thickness ratio at 2.5 and 7.5 cmwas determined to be r=1.7.

Example 14

To verify this, a second experiment was performed with a ratio ofureadmapa/guanadmapa =3/1 was performed.

28.6 g guanadmapa (0.125 mol) and 86.3 g ureadmapa (0.375 mol) weredissolved in 195 mL H₂O and heated to 96° C. 78.7 g/49.2 mL TMCB wereadded within 20 min and the mixture was refluxed at 100-103° C. for 3½h. After cooling to room temperature, a clear, colorless viscoussolution was obtained.

A Hull Cell test, in accordance with the Hull Cell plating test ofExample 2 (3 A/5 minutes), was performed using the material. The Hullcell test yielded panels that were similar in aspect to the onesobtained with the 1:1 ratio. The metal distribution was only slightlyimproved. The thickness ratio between measurements taken at 2.5 and 7.5cm from the left edge of the panels depending on the exact conditionswas r=1.5-1.7.

From the above description of the invention, those skilled in the artwill perceive improvements, changes and modifications. Suchimprovements, changes and modifications within the skill of the art areintended to be covered by the appended claims.

Having described the invention, the following is claimed:
 1. A zinc orzinc alloy electroplating bath comprising: zinc ions and a brighteningagent, the brightening agent comprising at least one polyamine or amixture of polyamines, the at least one polyamine or mixture ofpolyamines including a first repeating unit that has the generalformula:

and a second repeating unit selected from the group consisting of

and combinations thereof; where Δ₁ is O, N, or S; Δ₂ is O, N, or S, andΔ₂≠Δ₁; x is an integer from 2 to 6; y is an integer from 1 to 6; z is aninteger from 1 to 6; R₁, R₂, R₃, and R₄, which is the same or different,is methyl, ethyl, isopropyl, n-propyl, hydroxyethyl, or—CH₂CH₂(OCH₂CH₂)_(m)OH; m is a number between 0-6; R₅ represents a groupof atoms necessary to complete a heterocyclic compound having a five orsix membered ring containing at least two nitrogen atoms; and R₆ isnothing or an alkyl group.
 2. The zinc or zinc alloy electroplating bathof claim 1, the first repeating unit having the following formula:


3. The zinc or zinc alloy plating bath of claim 1, the brightening agentcomprising a mixture of polyamines, the mixture of polyamines includinga first polyamine of the general formula:

and a second polyamine of the general formula:


4. The zinc or zinc alloy plating bath of claim 1, the brightening agentcomprising a mixture of polyamines, the mixture of polyamines includinga first polyamine of the general formula:

and a second polyamine of the general formula:


5. The zinc or zinc alloy electroplating bath of claim 1, the firstrepeating unit and the second repeating unit being in the same polymerchain.
 6. The zinc or zinc alloy electroplating bath of claim 1, thepolyamine including a repeating unit having the following generalformula:

where R₇ is an alkylene group.
 7. The zinc or zinc alloy electroplatingbath of claim 1, the polyamine including a repeating unit having thefollowing general formula:

where v is an integer greater than
 1. 8. The zinc or zinc alloyelectroplating bath of claim 1, the polyamine including a repeating unithaving the following general formula:


9. The zinc or zinc alloy electroplating bath of claim 1, the polyamineincluding a repeating unit having the following general formula:


10. A zinc or zinc alloy electroplating bath comprising: zinc ions and abrightening agent, the brightening agent comprising at least onepolyamine or a mixture of polyamines, the at least one polyamine ormixture of polyamines including a first repeating unit that has thegeneral formula:

and a second repeating unit selected from the group consisting of:

and combinations thereof; where Δ₁ is O, N, or S; Δ₂ is O, N, or S, andΔ₂≠Δ₁; x is an integer from 2 to 6; y is an integer from 1 to 6; z is aninteger from 1 to 6; R₁, R₂, R₃, and R₄, which is the same or different,is methyl, ethyl, isopropyl, n-propyl, hydroxyethyl, or—CH₂CH₂(OCH₂CH₂)_(m)OH; m is a number between 0-6; R₅ represents a groupof atoms necessary to complete a heterocyclic compound having a five orsix membered ring containing at least two nitrogen atoms, and R₆ isnothing or an alkyl group.
 11. The zinc or zinc alloy electroplatingbath of claim 10, the second repeating unit comprising:


12. The zinc or zinc alloy electroplating bath of claim 10, the secondrepeating unit comprising:


13. The zinc or zinc alloy electroplating bath of claim 10, the secondrepeating unit comprising:


14. The zinc or zinc alloy plating bath of claim 10, the brighteningagent comprising a mixture of polyamines, the mixture of polyaminesincluding a first polyamine of the general formula:

and a second polyamine selected from the group consisting of:


15. The zinc or zinc alloy electroplating bath of claim 10, the firstrepeating unit and the second repeating unit being in the same polymerchain.
 16. The zinc or zinc alloy electroplating bath of claim 10, thepolyamine including a repeating unit having the following generalformula:

where R₇ is an alkylene group.
 17. The zinc or zinc alloy electroplatingbath of claim 10, the polyamine including a repeating unit having thefollowing general formula:

where v is an integer greater than
 1. 18. The zinc or zinc alloyelectroplating bath of claim 10, the polyamine including a repeatingunit having the following general formula:


19. A brightening agent for an alkaline zinc or zinc alloyelectroplating bath, the brightening agent comprising a copolymer of afirst monomer having the following formula:

and at least two of the following compounds selected from the groupconsisting of:

where Δ₁ is O, N, or S; Δ₂ is O, N, or S, and Δ₂≠Δ₁; x is an integerfrom 2 to 6; R₁, R₂, R₃, and R₄, which is the same or different, ismethyl, ethyl, isopropyl, n-propyl, hydroxyethyl, or—CH₂CH₂(OCH₂CH₂)_(m)OH; m is a number between 0-6; R₅ represents a groupof atoms necessary to complete a heterocyclic compound having a five orsix membered ring containing at least two nitrogen atoms; R₆ is nothingor an alkyl group; R₇ and R₈, which may be the same or different, is analkylene group; and X₁, X₂, and X₃, which is the same or different, is ahalogen.